Electrical apparatus



July 24, 1956 s. FOLDES ELECTRICAL APPARAT 3 Filed Sept. 30, 1955 INVENTOR.

amma ATTO NEYS United States Patent 1 2,756,351 ELECTRICAL APPARATUS Stephen Foldes, Endicott, N. Y., assignor to Bendix Aviafion Corporation, New York, N. Y., a corporation of Delaware Application September 30, 1953, Serial No. 383,207

21 Claims. (Cl. 307-150) This invention relates to electrical apparatus and more particularly to voltage control means for use between power sources and electrical energy consuming devices.

One of the objects of the present invention is to provide novel electrical apparatus which will supply a relatively constant voltage when connected through the same terminals to any of several sources of electrical energy having different output voltages.

Another object of the invention is to provide novelly constructed apparatus which will function to automatically detect within pre-determined limits the kind and magnitude of voltage supplied thereto and convert the same to an output voltage of pre-determined kind and magnitude.

A further object is to provide novel electrical apparatus wherein a relay switch arrangement is adapted to automatically select different circuits for operation when the input terminals are connected to different sources of electrical energy.

The above and further objects and novel features of the present invention will more fully appear from the following detail description when the same is ready in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for purposes of illustration only and is not intended as a definition of the limits'of the invention.

In the drawing, the single figure is a circuit diagram which illustrates one form of electrical apparatus embodying the invention.

Although the invention may be adapted for use with a wide variety of source voltages for conversion to a preselected output voltage, the illustrated embodiment will be described, in the interest of clarity, as a unit which is useful on or about modern commercial and military vehicles. One practical use for the illustrated device is between a cathode ray oscillograph type of ignition analyzer of known construction and the source of electrical power therefor. On or about commercial and military aircraft, tanks, automobiles and the like, there are generally available D. C. battery voltages ranging from about 6 to 28 volts and A. C. voltages ranging from about 100 to 120 volts at frequencies ranging from about 60 to 400 cycles/ second. The illustrated circuit will accordingly be described, by way of example, as embodying different circuits for input voltages of about 6, 12 and 24 volts D. C. and 115 volts A. C. to provide an output voltage of about 100 to 120 volts A. C. at a frequency of about 120 cycles/ second on D. C. input and at line frequency on A. C. input.

In the form shown, the novel unit comprehended by the invention comprises two input terminals A and B which may be pin or socket contacts of an electrical connector adapted for connection to the terminals of a source of electrical energy (not shown). The output terminals AC and BD may also be in the form of plug and socket connector contacts adapted to be connected to an electrical energy consuming device, such as an ignition analyzer. Terminal AC is permanently connected through leads 10, 11 and 12 to input terminal A and through leads and 14 to terminal C of the secondary winding 15 of a transformer 16. Output terminal ED is normally connected to ice the other terminal D of said secondary winding through a lead 17, a switch 18 and lead 19. When switch 18 is actuated to its lower position, output terminal BD will be connected to input terminal B through lead 17, switch 18 and leads 20, 21, 22 and a manually operable switch 23.

The basic elements of the illustrated unit include in series with manually operable switch 23 a plurality of relay operated, two-position switches 24, 25, 26, and 27, which are, like switch 18, resiliently actuated to a normal or up position (as shown in the drawing) and actuatable by relay coils 28, 29, 30 and 31, respectively, to their other or down positions, as seen in the drawing. These relay coils are connected in parallel across the input terminals or power supply line AB with a condenser 32 in series with coil 28 and a resistance 33 in series with coil 29. In the supply circuit to the D. C. relay coils 29, 30 and 31, there is also provided a choke coil which serves to prevent possible energization and action of the D. C. relays before operation of relay 28 when an alternating current supply is connected across terminals AB. In the system described, a coil having an inductance of about 15 millihenries and a D. C. resistance of about .25 ohm may be used. For a purpose to more fully appear hereinafter, relay coils 30 and 31 in conjunction with switches 26 and 27 are time delay relays. By way of example, the relays embodying coils 29 and 34, which may be combined into a single coil, are designed to be responsive to voltages in the vicinity of not les than about 24 volts D. C. and the relays involving coils 30 and 35 are responsive to voltages in the vicinity of not less than about 12 volts D. C. The relay coils 31 and 36 may, for example, be designed to be responsive to voltages not less than about 6 volts D. C. As pointed out above, these various relays may be designed for response to any pre-selected minimum voltage. Relay coil 28 is responsive to the line or input voltage when it is in the vicinity of to volts A. C.

When D. C. voltage is impressed across the input terminals A and B, one of the coils 34, 35 or 36, depending upon the input voltage, will be energized to colse one of the three circuits through vibrator 37, and various parts of the primary winding 38 of transformer 16, as will be hereinafter pointed out in more detail. These circuit closures are effected through a pair of switches 40 and 41, 42 and 43, or 44 and 45 which may be actuated to closed position by coils 34, 35 and 36, respectively, and to open position by suitable resilient means, not shown. Vibrator 37, which includes a resilient electrically conductive contact carrying reed 46 receives its energy from the input source through one of switches 47, 48 and 49, which are normally open but actuatable to closed position in the illustrated embodiment by relay coils 34, 30 and 31, respectively, when the latter are energized. If desired, one or more of the last-mentioned switches may be actuated by coils 29, 35 and 36, respectively.

As illustrated, vibrator 37 comprises two stationary contacts 50 and 51 connected through leads 52 and 53, respectively, to the abovementioned three pairs of switches including switches 40 and 41, and hence, to opposite sides of the center of primary winding 38 of transformer 16. The resilient electrically conductive reed 46 movably supports a contact 54 for alternate engagement with stationary contacts 50 and 51 in a manner well understood in the art and is connected through lead 21 to input terminal B. An induction coil 55 arranged to electromagnetically attract reed 46 downwardly is also connected at one end to the reed through separable contacts 57, 58 and hence, to input terminal B. The other end of coil 55 is connected through a lead 56 to a terminal of each of relay operated switches 47, 48 and 49, and hence, to input terminal A through common return lead 12 when any one of said switches is in closed position.

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Reed as carries the contact 57 which is adapted to normally engage spring mounted contact 58. The latter is connected in series with the coil 55 and hence, when c011- tacts 57 and 58 are engaged and one of switches 4-7, 48 and 49 is closed, current passes through coil 55 from source AB to cause actuation of the reed 46 downwardly. The latter thus swings its contact 54 into engagement with contact 50 and disengages contacts 57 and 58, thereby again de-energizing coil 55. Such deenergization permits reed 46 to spring to its uppermost position to engage contacts 54 and 51 as well as to re engage contacts 57, 58. The cycle is then repeated at a selected frequency.

Primary winding 38 of transformer 16 has its midpoint permanently connected through leads 11 and 12 to input terminal A. The ends of said primary winding are connected to switches 40 and 41 through leads 59 and 66, including resistors 61 and 62, respectively, and a condenser 63 is connected across the ends of said resistors remote from the primary winding 38. Switches 42 and 43 are also connected through leads 64 and 65 to opposite halves of primary winding 38 and switches 44 and 45 are likewise connected to coil 38 nearer the midpoint thereof by leads 66 and 67, respectively.

In considering the operation of the illustrated structure, let us first assume that the input voltage is 115 volts A. C. and that switch 23 is closed. Coil 23 will be energized through condenser 32 and effect actuation of switches 18 and 24 downwardly to the dotted line position as viewed in the drawing. Prior to actuation of switch 24 by coil 28, energization of coils 29, 34, 3t and 31 is effectively prevented by the action of choice 75. The relay coil 28 will continue to be connected across the source AB through switch 24 and a lead 68 while terminal B will be connected to output terminal BD through leads 22, 21 and 2%, switch 18 and lead 17. As previously pointed out, terminal A is permanently connected to output terminal AC through leads 1t 11 and 12; accordingly, the output terminals are connected directly across the source since switches 13 and 2.4 are relay actuated from their normal positions shown in full lines.

When the source voltage is D. C., coil 28 will not be affected because of the condenser 32 which blocks out direct current, but the voltage will be connected across relay coils 29, 30, 31 and 34 in parallel. if, with the examples heretofore assumed for purposes of description, the voltage is approximately 24 volts D. C., coils 29 and 34 will immediately react, thereby opening switch 25 and closing switches 46, 41 and 47. The character of time delay relays 30 and 31 is such that the same will not react to 24 volts as rapidly as coil 29 reacts thereto. Coils 30 and 31 may, for example, be designed to delay 12 and 60 seconds, respectively, when a voltage is impressed across the same. When coil 29 reacts and opens switch 25, the coils 30 and 31 will be thus disconnected from the source. With switches 46, 41 and 47 closed, vibrator coil 55 is connected across the source through switch 47 and opposite halves of primary winding 33 are alternately connected across the source AB through switches 40, 41 and vibrator contacts 50 and t. Accordingly, as reed 46 vibrates as described above, current will flow alternately and in opposite directions through opposite halves of the primary winding 38. This induces A. C. voltage in secondary winding and hence, across output terminals AC and BD, the magnitude of which voltage may be varied by varying the design of transformer 16.

When approximately 12 volts D. C. are connected across terminals A and B, the higher voltage coils 29 and 34 will not be affected, and the characteristics of coils 3t and 31 are such that the former will react first. Upon activation of coil 30, it is efiective to shift switch 26 to its lower position, thereby disconnecting coil 31 from the source and connecting relay coil 35 in live circuit. Coil 35 is thus rendered efiective to close switches 42 and 43. Switch 48 is also closed by coil 30, thereby activating the vibrator which closes circuits alternately through portions a and a of the transformer primary 38 to induce the desired output voltage across secondary winding 15.

If the voltage of the D. C. source is of the magnitude of approximately 6 volts, only relay coil 31 will be initially afiected and activated to close switches 27 and 39. The circuit through switch 49 activates the vibrator and coil 36 is activated through switch 27. Energized coil 36 closes relay switches 44 and 45 so that portions b and b of the transformer winding will be alternately connected to the source through the vibrator contacts to produce the desired output voltage.

it will thus be seen that when any of the several preselected source voltages are impressed across the input terminals A and B, the system hereinabove described functions automatically to supply a single A. C. voltage of pro-determined magnitude at the output terminals. If desired, additional relay sets could be added and similarly connected for response to other preselected voltages.

The resistors 61 and 62 in connection with condenser 63 limit the current build-up in winding 38 and provide filtering and power factor correction. This prevents excessive arcing at the vibrator contacts when the device is on '24-volt D. C. operation. If desired, a small light 70 may be connected in series with a resistor 71 across the output terminals for indicating the presence of voltage across these terminals. Condensers 72, 73 and 74 may be provided to reduce arcing across the vibrator contacts 5ll-54, 51--54 and 57-58.

In one satisfactorily operable system of the character herein described, the resistance 33 has a value of about 220 ohms, and resistances 61 and 62 have values of about .25 ohm each. Resistances 76 and 77 having values of about 6 ohms and 2 ohms, respectively, may be provided in circuit with switches 47 and 43, respectively. Condensers 32, 72, 73 and 74 each have capacities of the order of l microfarad, and the capacity of condenser 63 is of the order of about 10 microfarads. The resistance 71 has a value of about 1:. ohms. A suitable protective fuse 73 may be inserted in the supply line, or suitable smaller fuses may be used at other points in the circuit in accordance with the requirements of any particular system.

Although only a single embodiment of the invention is illustrated in the accompanying drawing and described in the foregoing specification, it is to be expressely understood that the invention is not limited thereto. For example, the number and values of the source voltages which may be impressed across the input terminals and accommodated by the system may vary widely, it being necessary only to provide suitable relays which may be properly chosen by any skilled artisan. Additionally, the voltage and frequency at the output terminals may be readily varied by adjusting the transformer and vibrator designs, and if it is desired to change the frequency of an alternating current source, this 'may be accomplished by incorporating suitable means for first converting the A. C. voltage to D. C. voltage and then reconverting the same through thevibrator and transformer to the desired A. C. voltage and frequency. Different known types of vibrators may also be used in lieu of the specific type illustrated and described. Various other changes may also be made, particularly in the design and arrangement of the parts and in the suggested electrical values of various parts, without departing from the spirit and scope of the invention as it will now be understood by those skilled in the art.

What is claimed is:

1. In electrical apparatus of the class described, a pair of input terminals, a pair of output terminals, means operable when alternating current voltage is' impressed across said input terminals to operatively connect the latter to said output terminals, a vibrator, a transformer, and means operable when direct current voltage is impressed across said input terminals to operatively connect the latter to said output terminals through said vibrator and transformer to impress alternating current voltage across the output terminals.

2. Apparatus as defined in claim 1 wherein said firstand second-named means include a plurality of relays comprising coils normally connected in parallel across said input terminals.

3. Apparatus as defined in claim 2 comprising a condenser in series with the relay coil of said first-named means.

4. Apparatus as defined in claim 2 comprising an in ductive choke in series with the relay coils of said secondnamed means.

5. Apparatus as defined in claim 2 comprising a switch operable by each of said relays for disconnecting from said source the coils of the other of said relays connected in circuit further from said source.

6. Apparatus as defined in claim 2 comprising switch means operable by the relay means of said first-named means for operatively connecting said input terminals directly to said output terminals.

7. Apparatus as defined in claim 2 comprising a vibrator, transformer means, and means rendered operable by each relay of said second-named means for connecting said vibrator and transformer means in series in a circuit for operatively conducting electrical energy from said input terminals to said output terminals.

8. Electrical apparatus of the class described comprising input terminals for selectively connecting the apparatus to any of a plurality of sources of electrical energy, output terminals for connecting said apparatus to a load, a plurality of normally open circuits for operatively connecting said input terminals to said output terminals, switch means for closing each of said circuits, and relay coils for efiecting operation of said switches, said coils being responsive to voltages of different kinds and magnitude for selectively closing said switches in accordance with the kind and magnitude of the voltage impressed across the input terminals to selectively connect the source and load through one of said circuits.

9. Apparatus as defined in claim 8 wherein said switch means effects a direct connection between said source and load when the source is of the alternating current variety.

10. Apparatus as defined in claim 8 comprising vibrator means and transformer means in some of said circuits for converting direct current energy to alternating current energy when the source is of the direct current variety.

11. Electrical apparatus for converting any of a plurality of D. C. voltages to A. C. voltage of pre-determined magnitude and frequency comprising input terminals for connection to a source of D. C. voltage, a plurality of relay coils connected in parallel across said input terminals, said coils being operatively excitable by different minimum voltages and each of said coils requiring a higher minimum excitation voltage than any of said coils which is connected in the circuit more remote from the source, switch means operable by each of said coils to interrupt the circuit to the other of said coils more remote from said source, a plurality of normally open circuits for conducting energy from said input terminals to said output terminals, and means operable in response to excitation of each of said coils to close one of said circuits, each of said circuits comprising a vibrator for interrupting the current at a pre-determined frequency and transformer means for converting the interrupted direct current to alternating current.

12. Apparatus as defined in claim 11 wherein the primary winding of the transformer means is center tapped and has opposite ends thereof connected to dilferent output terminals of said vibrator.

13. Apparatus as defined in claim 11 comprising switch means operable by each of said coils to disconnect from the source the other of said coils which are normally more remotely connected thereto.

14. In apparatus of the class described, a source of electrical energy, a plurality of relays having coils normally connected in parallel across said source, each of said relays being operably excitable by a lower minimum voltage than the other of said relays having coils connected in the circuit nearer to the source and each of said relays being operably excitable at different time intervals after connection to the source, the time delay of each relay being greater than the time delay of each of the other of said relays connected in the circuit nearer to the source, and switch means operable by each relay to disconnect from the source the other of said relays which are connected in the circuit further from the source.

15. Apparatus as defined in claim 14 comprising vibrator means, and means operable by said relays for selectively connecting said vibrator means and different parts of said transformer means in circuit with said source in accordance with the magnitude of the voltage thereof.

16. Apparatus as defined in claim 15 wherein said vibrator means alternately connects portions of opposite ends of the primary winding of said transformer means to said source, whereby alternating current is induced in the secondary winding of the transformer means.

17. In electrical apparatus, a source of direct current electrical energy, a load for consuming alternating current electrical energy, and means for transmitting electrical energy from said source to said load comprising vibrator means for interrupting direct current flow from said source, transformer means having primary and secondary windings, a plurality of pairs of circuits for alternately connecting portions of opposite ends of said primary winding to said source in series with said vibrator, means connected to and energized by said source for selectively closing one pair of said circuits in accordance with the magnitude of the voltage of said source, and means connecting the secondary winding of said transformer to said load.

18. Electrical apparatus as defined in claim 17 wherein said circuit closing means includes a plurality of induction coils normally connected to said source and selectively operably excitable in accordance with the magnitude of the voltage of said source.

19. Electrical apparatus as defined in claim 18 comprising switch means operable by each of said coils to interrupt the connections between said source and the other of said coils which are operatively excitable by said source.

20. Electrical apparatus of the class described, comprising input terminals for selectively connecting the apparatus to any of a plurality of sources of electrical energy, output terminals for connecting said apparatus to a load, a plurality of normally open circuits for operatively connecting said input terminals to said output terminals, switch means for closing each of said circuits, and relay coils for effecting operation of said switches, said coils being responsive to voltages of different magnitude for selectively closing said switches in accordance with the magnitude of the voltage impressed across the input terminals to selectively connect the source and load through one of said circuits.

21. Apparatus as defined in claim 20 comprising vibrator means and transformer means in said circuits for converting direct current energy to alternating current energy when the source is of the direct current variety.

References Cited in the file of this patent UNITED STATES PATENTS 2,127,488 Andrews Aug. 16, 1938 2,253,131 McGregor Aug. 19, 1941 2,420,609 Mitchell May 13, 1947 

